In the field of the transportable beverage cooling, hitherto, only cooling devices which operate in accordance with the compression principle, have been widely used. These compressor cooling devices essentially consist of a hermetically sealed compressor, an air-cooled condenser, a collecting container for the liquid CFC, a temperature controlled expansion valve, and a condenser. However, the "cold" generated in the evaporator of such devices, must be intermediarily stored in a "cold buffer."
In connection with compression cooling devices, commonly used "cold buffers" include either a water container with a water content of up to 20 liters, or are formed from a large aluminum block in order to provide desired cold storage. Notably, large aluminum block cold buffers have an advantage over the water container type cold buffer, in that the aluminum block type cold buffer does not need to be filled up with water before operating the compression cooling device. However, each such "cold buffer" has its shortcomings and drawbacks. In particular, the largest disadvantage of the aluminum block "cold buffer" is that the storage capacity is relatively small, so that during "beverage tapping" of more than 0.5 liter of beverage, the cooling effect of the cooling device is already exhausted. The water storage cold buffer is disadvantageous in that after filling it with water, the cooling device must be in use for a longer time period to precool the filled water storage itself. Moreover, the water container must be provided with an additional stirring means which pumps the water around the evaporator and cooling coils for a better heat exchange. This mechanical stirrer is rather susceptible to trouble and very often results in the breakdown of the total cooling device.
Such compression cooling devices described above, are used for cooling of beverages, such as beer, lemonades, etc., in party tents or otherwise during a party. The use of such compression cooling devices by a private person for cooling a beverage (e.g. in a rented beer barrel) has hitherto only been possible in a limited manner. This is due to the fact that the highly complex nature of such compression cooling devices requires that the user has a lot of technical know-how for proper operation. For the beverage merchant, such compression cooling devices cannot be profitably used in view of the high purchase and maintenance costs of such cooling devices.
In contrast to compression type cooling devices, there are a class of sorption devices which operate on fundamentally different set of thermodynamic principles.
In connection therewith, sorption devices are understood to mean devices wherein a liquid or sold sorption medium absorbs a second medium at a higher temperature and in the vapor state, by releasing heat. Before the operating medium is absorbed by the sorption agent, it evaporates under heat absorption in a cooling container. Thus, the evaporation temperatures are in the range of between -40.degree. and +40.degree. C., depending on the type of operating medium used and the field of use of the sorption medium.
Sorption apparatuses with solid adsorption mediums, referred to as "adsorption" apparatuses, operate periodically, that is, an adsorption phase is always followed by a desorption phase, wherein the operating medium (e.g. water) is again separated or driven off from the adsorption medium, e.g. zeolite. During the desorption phase, the operating medium cannot be absorbed and can therefore also not be evaporated. Hence, during the desorption phase, no cooling effect is generated (i.e. no absorption of heat is achieved) in the cooling container.
An example of a periodically operating adsorption cooling apparatus is disclosed in German Patent Application DE-OS 34 25 419. In such apparatus, an ice bank is generated in the cooling container during the adsorption phase by a partial evaporation of the water operating medium. As disclosed, the adsorption cooling apparatus includes an adsorption container which is filled with the adsorption medium, zeolite; a cooling container which contains the operating medium, water; and a shut off device, with the assistance of which, a steam or vapor conduit is closable between the adsorption container and the cooling container. Cold can be discharged over the surfaces of the cooling container for cooling, for example, a cooling bag, while heat can be discharged over the container walls of the adsorption container. During the desorption phase, the operating medium is desorbed from the adsorption medium by supplying desorption heat into the adsorption container and is subsequently condensed in the cooling container by releasing heat. After completion of this desorption process, the shut off device is closed and the adsorption container is allowed to cool. In this condition, the adsorption apparatus can be stored for any given length of time, for future use.
However, using prior art periodically-operating adsorption apparatus, hitherto it has been not possible to cool large amounts of liquid (e.g. beverage) down to temperatures between +4.degree. and +10.degree. C. independent of any given initial temperature thereof.
Accordingly, it is a primary object of the present invention to provide a sorption cooling system which is characterized by a simple and cost effective type of structure, which is capable of cooling with a very low control effort, large amounts of liquid down to temperatures between +4.degree. and +10.degree. C. starting from any given initial temperature.
Another object of the present invention is to provide a sorption cooler which employs a single charging station, which can be used to recharge discharged tranportable cooling units, each of which is detachable from the charging station after being recharged by desorption.
These and other objects of the present invention will become apparent hereinafter and in the claims.